When Mackey and Vendrell hook up with a cop from another precinct to investigate the shooting, Vendrell sets off an explosive confrontation with a suspect by making a racial slur. And Mackey seldom a paragon of restraint defuses the situation. But before this tense hour is over, Mackey’s complex relationship with Vendrell becomes even more complicated. Meanwhile, Dutch and Wyms search for a serial killer and bring in a psychic on a complaint from the son of one of her clients, and David calls internal affairs after getting Julien’s affidavit.